A Lava Planet Kept a Sky the Models Said It Should Have Lost

TOI-561 b is a rocky world about 280 light-years away whose year lasts a little over 10 hours. It is about 1.4 Earth radii and 2.2 Earth masses, density about 4.3 grams per cubic centimetre, and about 40 times closer to its star than Mercury is to the Sun. A bare rock in that orbit should sit near 2,700 degrees Celsius. It should have lost any thick atmosphere billions of years ago.

Lisa Dang's team watched it with the James Webb Space Telescope for 37 hours, nearly four orbits. The phase curve is too bright, and too even, for a naked lava ball. Anjali Piette at Birmingham says the fit is a reflective sky, possibly silicate clouds of silicon dioxide and magnesium silicate, acting as sunscreen. The feed, if the picture holds, is a planet-wide molten surface boiling rock into weather.

Key Evidence

• Sci.News and University of Waterloo coverage of a new James Webb analysis, late October 2026
• Planet: TOI-561 b, about 280 light-years out, orbital period a little over 10 hours
• About 1.4 Earth radii, 2.2 Earth masses, density about 4.3 g/cm³
• About 40 times closer to its star than Mercury is to the Sun
• Expected bare-rock temperature near 2,700 degrees Celsius
• Observation: 37 hours, nearly four orbits, led by Lisa Dang
• Anjali Piette: reflective atmosphere, possible silicate clouds

The Rational Explanation

A phase curve is a brightness budget, not a photograph of clouds. A different surface map, or a thinner haze, can mimic part of the same signal. Atmospheric escape models have been wrong about individual worlds before, usually because the model assumed a history the planet did not have. The sunscreen made of sand is a good fit. It is not a sample.

What We Don't Know

Whether the sky is thick, patchy, or a misread of the dayside rock. What the clouds are made of, beyond a mineral family. How a world that close kept anything. The textbook says cinder. The light says otherwise. The light has not yet been asked a second question.

The Rabbit Hole

Lava worlds were supposed to be the simple exoplanets: no air, no weather, a thermometer with an orbit. If this one has a sky made of boiled rock, the simple end of the catalogue is where the strange weather went to hide.